This post from Sadly, No! deserves attention:
Anyone with TiVo grab a copy of ABC News tonight? There's a brief segment with a truck driver outside of the Superdome. It might be on again during the late news.
Those are the guys we heard on the [New Orleans police] scanner. The one who was on ABC said that they were loaded and ready to go on Monday, and told not to leave. And then they arrived right as the President was doing his media circus.
This might be nothing, or it might put the lie (horribly) to the notion that it's the Left that's "playing politics" with the NOLA disaster.